青藏高原20种灌木抗旱形态和生理特征

该研究以青藏高原地区采集的柠条锦鸡儿(Caragana korshinskii)等20种灌木树种为研究对象, 将其二年生幼苗移栽至苗圃培育, 通过田间试验测定三年生苗木生物量根冠比(RSR)、叶片蒸腾速率(T_r)、瞬时水分利用效率(WUE_i)、稳定碳同位素组成(δ¹³C)、叶片解剖结构特征和根系特征(长度、表面积、体积和根尖数)指标, 综合分析其抗旱性能差异, 为青藏高原干旱地区灌木树种抗逆性(耐旱)评价指标的建立、优良抗逆性树种的筛选及各种灌木树种的合理立地配置提供必要的理论依据。研究结果表明: 所选20种灌木为适应长期的干旱逆境, 不同植物种具有不同的抗旱策略。研究中将灌木抗旱机制划分为6个类型: 根系特征抗旱型、叶片旱生结构型、叶片旱生形态型、生物量分配型、节水型、高水分利用效率型。不同属和同属不同种灌木抗旱性有所差异, 沙棘属(Hippophae)植物总体抗旱性不佳, 而金露梅(Potentilla fruticosa)、豪猪刺(Berberis julianae)、树锦鸡儿(Caragana arborescens)、绣线菊(Spiraea salicifolia)和蒙古沙棘(Hippophae rhamnoides ssp. mongolica)综合抗旱性能较好, 总体上属于根系和叶片抗旱特征明显、低耗水、高生产效率的抗旱性强树种, 可以在青藏高原地区植被恢复树种筛选时优先考虑。根系特征值之间存在极显著正相关关系, 叶片结构特征指标之间也存在不同程度的相关关系, 但RSR、T_r、WUE_i和δ¹³C与根系特征值和叶片解剖结构特征指标之间总体上相关性不显著。主成分分析结果显示灌木全根和细根的长度、表面积、体积、根尖数和叶片栅栏组织厚度、海绵组织厚度、瞬时水分利用效率因子载荷较高, 能较好地反映青藏高原灌木树种抗旱性差异相关信息。此外, 灌木树种原产地与抗旱性也存在一定的联系, 青海西宁地区采集的灌木树种总体抗旱性优于甘肃天水和西藏拉萨地区。     

生境适宜度指数模型研究进展

生境适宜度指数(habitat suitability index,HSI)模型作为一种生境评价方法,在土地管理规划和评估中得到大量应用.本文总结了HSI模型在野生动物生境评价中的开发及应用,重点介绍了利用3S技术进行HSI建模及与其他模型耦合进行生境评价的现状;阐述了利用多种统计方法对HSI模型的评估和验证;探讨了HSI模型在主观性和非通用性等方面存在的问题和局限性,最后,就HSI模型在野生动物生境评价中的发展前景进行了展望.     

陇中黄土高原春小麦光谱反射特征

通过田间小区试验,测定了3个春小麦品种(高原602、陇春8139和定西24)在不同生育期和不同种植密度的光谱反射率及对应叶面积指数(LAI)和地上生物量,分析了其光谱反射的一般特征和红边参数特征以及光谱变量与LAI和地上生物量的相关性.结果表明:在整个波段内,春小麦冠层光谱表现为高原602＞陇春8139＞定西24,其叶片光谱表现为定西24＞陇春8139＞高原602;春小麦冠层光谱在可见光波段和中红外波段成熟期明显大于孕穗期,而叶片光谱在近红外波段孕穗期明显大于成熟期;随着种植密度的提高,在近红外波段冠层和叶片的光谱反射率逐渐增加;冠层光谱的红边均具有"双峰"现象,从孕穗期到成熟期,冠层红边位置呈现"蓝移"现象;LAI和地上生物量与冠层光谱变量之间存在较好的相关性.     

Cladogenesis and phylogeography of the lizard Phrynocephalus vlangalii (Agamidae) on the Tibetan plateau

Phrynocephalus vlangalii is restricted to dry sand or Gobi desert highlands between major mountain ranges in the Qinghai (Tibetan) Plateau. Mitochondrial DNA (mtDNA) sequence (partial ND2, tRNA(Trp) and partial tRNA(Ala)) was obtained from 293 Phrynocephalus sampled from 34 sites across the plateau. Partitioned Bayesian and maximum parsimony phylogenetic analyses revealed that P. vlangalii and two other proposed species (P. erythrus and P. putjatia) together form a monophyletic mtDNA clade which, in contrast with previous studies, does not include P. theobaldi and P. zetangensis. The main P. vlangalli clade comprises seven well-supported lineages that correspond to distinct geographical areas with little or no overlap, and share a most recent common ancestor at 5.06 +/- 0.68 million years ago (mya). This is much older than intraspecific lineages in other Tibetan animal groups. Analyses of molecular variance indicated that most of the observed genetic variation occurred among populations/regions implying long-term interruption of maternal gene flow. A combined approach based on tests of population expansion, estimation of node dates, and significance tests on clade areas indicated that phylogeographical structuring has been primarily shaped by three main periods of plateau uplift during the Pliocene and Pleistocene, specifically 3.4 mya, 2.5 mya and 1.7 mya. These periods corresponded to the appearance of several mountain ranges that formed physical barriers between lineages. Populations from the Qaidam Basin are shown to have undergone major demographic and range expansions in the early Pleistocene, consistent with colonization of areas previously covered by the huge Qaidam palaeolake, which desiccated at this time. The study represents one of the most detailed phylogeographical analyses of the Qinghai Plateau to date and shows how geological events have shaped current patterns of diversity.     

基于叶绿体DNA trnL-F序列研究肋果沙棘的谱系地理学

由于青藏高原的地理效应,第四纪冰期气候的反复变化应对现今该地区生物的地理分布及其居群遗传结构产生重大影响。肋果沙棘Hippophae neurocarpa是青藏高原地区的一个特有种,根据叶上的附属物（星状鳞毛或者鳞片状鳞毛）分为两个亚种：肋果沙棘亚种subsp.neurocarpa和密毛肋果沙棘亚种subsp.stellatopilosa。依据母系遗传的叶绿体DNA片段对该物种谱系地理学进行研究不仅能阐明该物种冰期避难所,而且对于理解两个亚种的母系分化也具有重要意义。共对两个亚种14居群的70个个体的trnL-F序列进行了测序,共发现8种单倍型,其中5种单倍型出现在肋果沙棘亚种中,4种出现在密毛肋果沙棘亚种中,两个亚种共享一种单倍型。种内谱系分化与两个亚种形态上的分化不一致。嵌套进化分支把8种单倍型分为三支：一支为肋果沙棘亚种,其他两支中两个亚种单倍型嵌套组成,且肋果沙棘亚种处于进化末端。我们的研究结果还表明肋果沙棘在冰期可能在高海拔地区存在多个避难所,并且存在来自避难所的邻域扩张。     

Magnetic signature of environmental change reflected by Pleistocene lacustrine sediments from the Nihewan Basin, North China

A mineral magnetic study has been conducted on Pleistocene lacustrine sediments from the Xujiayao Paleolithic site within the Nihewan Basin, North China. The magnetic signal is characterized by a dominance of high-coercivity (hematite) minerals that is modulated by low-coercivity magnetite–maghemite assemblages during interglacials. A high-amplitude record of the composition dependent magnetic S_− 0.3 T-parameter varies in accord with composite marine oxygen isotope records, suggesting climate modulation of magnetic composition. The Xujiayao site is situated at the northern outskirts of the Chinese Loess Plateau (CLP) and has neither received significant eolian input nor been exposed to pedogenic processes comparable to those acting on CLP. Mineral magnetic analyses suggest that variations in both magnetite and hematite are primarily controlled by detrital fluxes rather than by authigenic production of magnetic minerals. Here we propose that the fluctuations of magnetic signals at Xujiayao are not derived from varying compositions of eolian flux with glacial/interglacial periods or minute eolian influx during interglacials, but is likely dominated by runoff-related processes, by which some weathered/pedogenized loess and soils with stronger magnetic signals have been eroded and transported to the catchment during interglacials resulting in magnetic enhancement. The inferred continuous deposition from the Brunhes/Matuyama boundary to the paleosol S₁ (ca. 129 ka) gives the age of ca. 500 ka for the sediments carrying the Xujiayao Paleolithic site, suggesting an allogenic origin of the Paleolithic artifacts and mammalian bones dated by U–Th method to ca. 100 ka.     

长期施肥条件下黄土旱塬土壤N03^--N的淋溶分布规律

在黄土旱塬区,长期施肥对土壤剖面NO3^-1—N含量和分布有显著影响．施用化学氮肥,土壤剖面中出现NO3^-1—N的淋溶与深层累积,而施用磷肥和有机肥有减弱NO3^-1—N向更深层淋溶的作用．单施氮肥处理(N),NO3^-1—N的累积峰深度最大,为120～200cm;N、P有机肥配施处理(NPM),NO3^-1—N的累积峰值最高,但峰深度降低至60～120cm;N、P配施(NP)累积深度为80～140cm．不施氮肥,分布在土壤剖面中NO3^-1—N含量显著降低．氮肥用量愈大,NO3^-1—N的累积量愈大．N、P配施可以有效降低NO3^-1—N累积．在同一氮肥用量下,NO3^-1—N累积量随磷肥用量的增加而减少．     

黄土高原刺槐林生长与土壤水分关系研究进展

从林地土壤水分、刺槐生长、土壤水分与刺槐生长关系、土壤水分与根系分布的研究四个方面介绍了近十几年来黄土高原刺槐林生长与土壤水分关系研究的最新进展。     

Distribution,species diversity and life-form spectra of plant communities along an altitudinal gradient in the northern slopes of Qilianshan Mountains,Gansu, China

We studied the distribution pattern, species diversity and life-formspectra of plant communities along an altitudinal gradient in the mid-sectionofthe northern slopes of Qilianshan Mountains by means of multivariate analyses.Two data sets (167 species × 75 plots, 10 environmental variables ×75 plots), originated from the fieldworks in 1998–1999, were subjected toTWINSPAN and DCCA, resulting in 8 major plant communities: 1)Asterothamnus centraliasiaticus–Halogetonarachnoideus desert grassland on azonal substrates from 1450 to 1600m and 2) zonal Reaumuria soogorica desertgrassland on gravels from 1470 to 1900 m; 3) Stipaprzewalskii–Stipa purpurea montane grassland from 2200 to 2900m; 4) Polygonum viviparum alpine grasslandfrom 2900 to 3700 m; 5) Caraganastenophylla–Ajaniafruticulosa dry-warm shrubland from 2350 to 2800 m; 6)Sabina przewalskii mid-wet warm forest from 2700 to 3300m; 7) Picea crassifolia cold coniferousforestfrom 2450 to 3200 m; 8) Caragana jubatawet-cold alpine shrubland from 3100 to 3700 m. Species diversityand species richness of both grasslands and forests peaked at the intermediateportion of the elevational gradient. Evenness might be strongly influenced byeither biotic or abiotic factors at a local scale, while seems quiteindependentof an elevational gradient at landscape scales. Beta-diversity decreased from1500 to 3700 m, indicating that species turnover declined withincreased elevation. Both richness of life-form and total species richness in agiven altitudinal belt (gamma-diversity) peaked at intermediate elevations,while relative species richness of different life-form varied differently alongthe altitudinal gradient.     

High genetic differentiation and low genetic diversity in Incarvillea younghusbandii, an endemic plant of Qinghai-Tibetan Plateau,revealed by AFLP markers

Incarvillea younghusbandii Sprague (Bignoniaceae) is a perennial herbaceous plant endemic to Qinghai-Tibetan Plateau. As a species of medical and horticulture importance, I. younghusbandii is threatened by over exploitation and habitat fragmentation. In this study, we analyze the genetic diversity and population structure of I. younghusbandii using amplified fragment length polymorphism (AFLP) markers. Our data reveal very low levels of genetic diversity in seven natural populations across Tibet. Specifically, at population level, the average Nei's genetic diversity index (H_E) and Shannon's diversity index (I) were 0.063 and 0.096, respectively. In contrast, high genetic differentiation among populations (Gst = 0.6238, Φ_ST = 0.614) is detected. The results of Neighbor-joining cluster, PCO, and STRUCTURE assignment reveal consistent pattern, suggesting seven well-defined genetic groups that are concordant with their geographical origins. The possible mechanisms and implications of these findings for conservation are discussed.